Recently, magneto-optical disks and magneto-optical disk recording/reproduction devices adopting so-called the external clock method, that is, the method in which marks having phase information (hereinafter referred to as clock marks) are preformatted in a magneto-optical disk, a clock in bits (hereinafter referred to as a channel clock) is generated by a phase synchronization loop [PLL (Phase Locked Loop)] circuit using a reproduction signal of the clock marks, and the channel clock is used for recording/reproduction, have been proposed.
However, since a processing path for generating the channel clock and a processing path for a reproduction signal of recorded data are different, a phase difference is caused.
Therefore, conventionally, phase correction to delay the channel clock by a delay amount corresponding to the phase difference between the phase of the channel clock and the phase of reproduction data from a record pit is carried out at the time of reproduction.
The optimum value of the delay amount varies depending on a device used for recording, or the ambient temperature, etc. Therefore, as shown in FIG. 9, first, a fixed pattern area 103 is provided in each sector 102, and a predetermined fixed pattern 106 is recorded in the fixed pattern area 103 at the same time when recording record data. Then, a phase difference between a fixed pattern reproduction signal FP and a channel clock CCLK is detected, and the delay amount is determined by the phase difference. This method has been generally used.
Besides, it has been carried out that a block 101 for completing error correction processing [hereinafter referred to as an ECC (Error Correction Code) block] is provided so as to include a plurality of the sectors 102, in order to improve durability against a burst error and increase a data usage ratio of a recording medium. In this case, since the ECC block 101 is the minimum recording unit, a plurality of the sectors 102 are recorded at a virtually same time, by the identical device.
When recording/reproducing a magneto-optical disk in the foregoing format, in a magneto-optical disk recording/reproduction device, as shown in FIG. 10, a clock mark reproduction signal 104 reproduced from a magneto-optical disk 111 by a pick up 112 is changed to a clock mark binarization signal 105 by a signal processing circuit 113, and is inputted to a PLL circuit 114. In the PLL circuit 114, the channel clock CCLK synchronizing with the clock mark binarization signal 105 is generated, and the channel clock CCLK is inputted to a phase control circuit 115.
On the other hand, a reproduction signal of record data reproduced from the magneto-optical disk 111 by the pick up 112 is inputted via the signal processing circuit 113 to an AD converter 116, and is sampled based on a sampling clock SCLK outputted from the phase control circuit 115, which will be mentioned later. An output of the AD converter 116 is inputted to a phase difference detection circuit 117, and the phase difference detection circuit 117 detects a phase difference between the sampling clock SCLK and the fixed pattern reproduction signal FP for each bit using the inputted data after AD conversion, calculates a shift average, and outputs the average as phase difference data 107. The phase difference data 107 is inputted to a holding circuit 118.
To the holding circuit 118, a fixed pattern area identification signal FPA is inputted. Therefore, the holding circuit 118 identifies the fixed pattern area 103 by using the fixed pattern area identification signal FPA, holds the phase difference data 107 of the fixed pattern area 103, and outputs the phase difference data 107 to the phase control circuit 115. The phase control circuit 115 delays the channel clock CCLK inputted from the PLL circuit 114 according to the held phase difference data 107, and outputs the sampling clock SCLK whose phase is controlled.